KIEV, Feb. 27 - Russian-backed separatists in Ukraine on Monday threatened to seize control of enterprises across their territories unless Kiev halts a blockade by nationalist protesters, AFP reported.

The leaders of the self-proclaimed Donetsk and Luhansk People's Republics said they would install "external managers" at industries on their turf if Kiev did not end the month-long blockade by Wednesday.

The blockade by nationalist activists angered over Ukraine trading with the coal-rich insurgent-controlled east has disrupted trade and threatened power supplies to the rest of the country.

Since Moscow-backed rebels grabbed control over swathes of the industrial east at the start of a war in 2014 the heavy enterprises there that provide most of the work have been trapped in a legal grey zone.

Trade with the rebel regions has gone on even as Kiev and the separatists are locked in a 34-month conflict that has claimed more than 10,000 lives.

In order to continue trading with the rest of Ukraine the firms have been registered legally in government controlled areas but pay taxes to both the rebels and the central government.

Ukraine is also suffering from the nationalist coal blockade as fuel supply problems at power plants have sparked fears of outages.

But Kiev remains reluctant to use force against strikers who accuse officials of trading with the foe as well as allowing contraband to reach the east from Ukraine.

As the dispute over the blockade heated up there were more deadly clashes between the two warring sides along their volatile frontline.

Ukraine's army said two of its soldiers were killed and another four wounded in despite a supposed truce coming into force last week.

On Sunday, the United States called on Russia to "immediately" observe the ceasefire in Ukraine, accusing combined Russian and separatist forces of targeting international monitors.

Ukraine and the West accuse Moscow of masterminding the uprising in a bid to keep Kiev under its heel following the ouster of a Russian-backed leader there in 2014. The Kremlin denies involvement. (afp/ez)